(a) Field of the Invention
The present invention relates to a method and apparatus for protection switching. More particularly, the present invention relates to a method and apparatus for protection switching in a point-to-multipoint network.
(b) Description of the Related Art
Protection switching is a method of most quickly resuming traffic when traffic is stopped as an obstacle occurs in a network. Protection switching is classified into linear protection switching and ring protection switching according to topology of a network, and the linear protection switching is classified again into 1+1, 1:1, 1:N, or M:N protection switching.
A basic protection switching method is a method of setting another traffic path (hereinafter referred to as a “protection path”) between end points in order to protect a traffic path (hereinafter referred to as a “working path”) between end points with a 1+1 method. In this method, a transmitting terminal normally transmits traffic using both a working path and a protection path, and a receiving terminal receives traffic from a working path and selects a protection path and receives traffic when an obstacle occurs in the working path. The protocol is simple in this method, but half of a network resource is wasted for a protection path.
The 1:1 method allocates one protection path for one working path, as in the 1+1 method. However, this method normally transmits traffic using only a working path and uses a protection path when an obstacle has occurred in the working path. Because the protection path may be normally used for transferring less important traffic that does not require protection switching, the 1:1 method is more efficient than the 1+1 method.
The M:N method allocates M number of protection paths in order to protect N number of working paths. This method is an invented method in order to use a network resource more efficiently than the 1:1 method, and when M is smaller than N, efficiency thereof increases. However, the M:N method can protect traffic of obstacles of the M number or fewer in the N number of working paths.
The 1:N method is a special case where M=1 in the M:N method, and an operation principle of the 1:N method is the same as that of the M:N method.
Such a linear protection switching method is applied to protection switching in a point-to-point network, sets a working path and a protection path to not meet for traffic that is transmitted in a bi-direction or one direction between points, and in the method, traffic is normally transmitted to the working path, and when an obstacle occurs in the working path, or according to an operator's instruction, traffic is transmitted to the protection path.
In a point-to-multipoint point network, a ring protection switching method is generally used. Therefore, it is difficult to use an existing linear protection switching method in a rooted multipoint connection network.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.